Interstitial cystitis (IC) is a bladder hypersensitivity disease associated with bladder pain, which has been a major challenge to understand and treat. We hypothesize that targeted and localized expression of endogenous opioid peptide in the bladder could be useful for the treatment of bladder pain. Pro-opiomelanocortin (POMC) is one of such precursor molecules for an opioid peptide, beta-endorphin. In this R21 grant proposal, using a gene-gun method for the transfer of POMC cDNA in vivo that we have recently developed, and investigated its efficacy and safety on acetic acid and cyclophosphamid-induced bladder hyperactivity in the rats. Human POMC cDNA was cloned into a modified pCMV plasmid. We will deliver the cDNA into the bladder wall of adult female rats by direct injection or gene-gun. We will evaluate short and long-term effects of this form of therapy with acute and chronic bladder hyperactivity models using acetic acid and cyclophosphamid. Physiological testing with cystometrograms and immunohistochemical testing will be used to detect endorphin after POMC cDNA transfer. We believe that POMC gene can be transferred in the bladder using gene-gun and that increased expression of endorphin in the bladder can suppress nociceptive responses induced by bladder irritation. Thus POMC gene-gun, delivered through the working port of a cystoscope, may be useful for the treatment of IC and other types of visceral pain. The long-term objective of this R21 project is to develop convincing data to justify a RO1 submission within the two years time frame of the project. Moreover, we want to establish a safe and effective concept of nonviral gene therapy for the treatment of the painful bladder syndromes. This research project is important to provide a solid basis for potential future clinical application.